In the United States, every two seconds that elapses a different person is in need of a blood transfusion. Blood cannot be artificially manufactured and can come only from human donations. As a result, over 15.7 million blood donations are made per year. The donated blood is collected, processed, and stored until required for use.
Donated blood is collected as whole blood, which consist of red blood cells, platelets, plasma and cryoprecipitate. Whole blood may be processed, stored, and used as is, or it may be separated into its component parts and then processed for storage and use. After processing, whole blood and red blood cells can be stored for up to 42 days at between two (2) and six (6) degrees Celsius. Platelets must be used within five days of collection. Plasma and cryoprecipitate may be stored in a frozen state for up to one year after collection.
As donated blood or blood components are refrigerated for storage, new units added to the cooler could potentially transfer their heat to nearby units as well as the cooled air, creating undesirable consequences for the refrigeration and storage process. Such heat transfer between units may negatively affect the storage life of the blood or blood components.
Donated whole blood, or the components thereof, is delivered from blood banks to hospitals in its stored state. Whole blood is delivered with a temperature between two (2) and six (6) degrees Celsius and plasma and cryoprecipitate are delivered frozen with a temperature below negative twenty (−20) degrees Celsius. For whole blood, cold blood may be transfused without any ill effect if administered at a slow rate. However, for rapid transfusions of a large volume of blood it is recommended that the blood be brought to an appropriate temperature to avoid any complications, such as hypothermia. Whole blood should never be rapidly brought to temperature in a water bath, in hot towels, or close to a heating device as this could lead to extensive hemolysis and serious transfusion reactions. The frozen plasma and cryoprecipitate must be thawed before use. Frozen plasma and cryoprecipitate may be thawed using water baths, but must be monitored to ensure precise control of the water temperature to ensure uniform thawing to avoid damage.
Blood warmers are available to raise the temperature of whole blood to an appropriate temperature for use. Blood warmers are typically limited to bringing to temperature a single unit of whole blood. The most common blood warmers now in use are in-line warmers, which are not adequate for rapid-transfusions of a large volume of blood at a high rate. The use of water baths for thawing plasma and cryoprecipitate requires constant monitoring as mentioned above. Additionally, the warming of multiple units of plasma and cryoprecipitate into a single water bath affects the heat transfer rate of the individual units. The addition of new frozen plasma and/or cryoprecipitate units into an existing water bath with partially thawed units will reduce the temperature of the water bath as the water bath equilibrates to a steady state temperature. The resulting lower temperature of the water bath may then lower the temperature of the partially thawed units while simultaneously raising the temperature of the frozen units. The use of a single water bath to thaw several units slows the overall heat transfer rate of each individual unit when compared to using a single water bath for a single unit.
Although, as explained above, the rate of heating blood for rapid, large-volume transfusions is a significant concern, insufficient attention has been paid to the cooling process. Since cold blood may be used without any negative effects in many transfusions, providing a more reliable way to cool blood or blood components and maintain a consistent temperature may have as significant an effect on transfusion success rate as improvements in heating blood. Additionally, storage lesion—biochemical and biomechanical changes to red blood cells which occur irregularly during storage—is a significant cause of poor transfusion outcomes regardless of the temperature at the time of transfusion. At the very least, a method or apparatus for thermally isolating individual units can reduce the risk and magnitude of quality degradation during the storage, transportation, and use of blood or blood components.
In light of the above, it would be advantageous to provide a blood carrier that is capable of thermally isolating individual compartments. It would further be advantageous to provide a blood carrier capable of warming or cooling multiple units simultaneously without affecting the heat transfer rates of the other units. It would further be advantageous to provide a blood carrier with which units of blood could be placed in a cooler and removed while minimizing effects on the temperature of the other units.